Messages in this thread | | | Date | Mon, 18 May 2009 09:34:12 +0100 | From | Ben Dooks <> | Subject | Re: [PATCH] [drivers] [SPI] SPI_GPIO: add support for controllers with missing MISO pin |
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On Mon, May 18, 2009 at 10:30:55AM +0200, Marek Szyprowski wrote: > Hello, > > On Thursday, May 07, 2009 2:32 PM Ben Dooks wrote: > > > On Thu, May 07, 2009 at 02:24:11PM +0200, Marek Szyprowski wrote: > > > There are some boards that do not strictly follow SPI standard and > > use only 3 wires (SCLK, MOSI, SS) for connecting some simple auxiliary > > chips and controls them with GPIO based 'spi controller'. In this > > configuration the MISO line is missing (it is not required if the chip > > does not transfer any data back to host). The example of such board is > > a NCP ARM S3C64XX based machine. This patch adds support for such non- > > standard configuration in GPIO-based SPI controller. > > [...] > > > diff --git a/drivers/spi/spi_gpio.c b/drivers/spi/spi_gpio.c > > > index 26bd03e..5b75601 100644 > > > --- a/drivers/spi/spi_gpio.c > > > +++ b/drivers/spi/spi_gpio.c > > > @@ -114,7 +114,10 @@ static inline void setmosi(const struct > > spi_device *spi, int is_on) > > > > > > static inline int getmiso(const struct spi_device *spi) > > > { > > > - return !!gpio_get_value(SPI_MISO_GPIO); > > > + if (SPI_MISO_GPIO) > > > + return !!gpio_get_value(SPI_MISO_GPIO); > > > + else > > > + return 0; > > > } > > > > Is zero a good approximation for 'no gpio' ? > > Now I found that zero might be a valid gpio pin number on some architectures > (it just means GPIO0 pin). This is imho a bit strange behavior of gpiolib as > there should be also a special values for INVALID or NOGPIO cases. Does > anyone have any ideas how such cases should be handled properly?
I belive there is a gpio_is_valid() function to tell you precisely if the given GPIO is valid.
-- Ben
Q: What's a light-year? A: One-third less calories than a regular year.
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